Conventional operating methods and control devices for such a method may be disadvantageous in that, on the one hand, they may lead to an increased contamination risk of the fuel injector and, on the other hand, they may prevent a controlled closing of the fuel injector.
The increased contamination risk is due to the fact that the fuel injector is in a state of a comparatively low lift of the injection needle, and thus reduced opening of the fuel injector, for a relatively long period of time. The danger that particles get jammed between the valve orifice and the valve needle and clog the valve orifice is especially great in this state.
A greater slope steepness of the trigger signal leads to greater velocity of the valve needle in the transition from the opening to the closing position and vice versa, but, due to the high velocity of the valve needle, so-called needle bouncers occur when the valve needle hits the valve seat, which cause the fuel injector to open in an uncontrolled manner after reaching the closing position. Furthermore, overswingers of the valve needle may occur.